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(1) Field of the Invention
This invention relates to wireless communications systems and more specifically to a diversity antenna for a UNII band access point.
(2) Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The Federal Communications Commission""s (xe2x80x9cFCCxe2x80x9d) promulgated rules for the Unlicensed National Information Infrastructure (xe2x80x9cUNIIxe2x80x9d) bands, 5.15-5.35 GHz and 5725 MHz to 5825 MHz. There are three UNII bands, each are 100 MHz bands. Of interest in the present application are the UNII-1 band, 5150-5250 MHz and the UNII-2 band, 5250-5350 MHz. The UNII-1 band is reserved for indoor wireless use. The UNII-2 band is designed for indoor or outdoor wireless LANs and allows for a higher powered, customizable antenna. By designing for the UNII-1 rules, the same system may be used on either UNII-1 or UNII-2. However, the FCC UNII rules require captured antennas for all products that operate in the UNII-1 band. Effectively, this rule does not allow a user to change antennas in the field.
Access Points (AP""s) benefit from a variety of antennas that may be chosen or spatially oriented to suit the installation. Most applications can be installed with either a dipole antenna for an omni-directional coverage pattern or an external patch antenna for a directional coverage pattern. AP""s and antennas may be mounted in a variety of environments. They may, for example, be mounted vertically on a wall, horizontally on a shelf, or hung from a ceiling.
Therefore, the need exists for an antenna system for UNII Access Points that conforms to the FCC UNII rules, offers the most flexibility in matching the characteristic of the antenna to the installation requirement, and has the benefits of a diversity antenna.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of instrumentalities and combinations particularly pointed out in the appended claims.
In view of the aforementioned needs, the invention contemplates a combination of a near omni-directional antenna (almost omni-directional in the H-plane), and an internal, configurable low gain patch array that are all built into the access point in accordance with the FCC requirements. The antenna system will be rotatable so that the correct antenna orientation can be achieved to allow for more optimal coverage. When deploying the near-omni antennas, the antenna system will be rotated to the vertical and when deploying the patches, the system will be rotated to the horizontal. The present invention essentially provides the flexibility to meet the needs of the majority of access point installations encountered. The higher frequency of the UNII bands, 5 GHz, makes smaller geometry antennas possible within the product envelope.
The near omni-directional antenna (near-omni antenna) will be constructed on the same printed circuit board (PCB) as the patch array. These antennas have a (roughly) 180 degree 3-dB beamwidth and only about 10 dB maximum side lobe suppression, mostly in the direction of the other near omni-directional antenna.
The directional antenna comprises a typical TM10 mode rectangular patch antenna, probably realized with a stacked parasitic element to meet bandwidth requirements. Size and other physical dimensions determine the characteristics of the TM10 mode stacked patch antenna array.
A means for selecting the antenna type (either omni directional or directional) may be provided by either a configuration utility at installation or a small mechanical detect switch could be utilized to sense the orientation of the antenna system. If the AP is mounted on the ceiling or on a bookshelf (or any horizontal mounting), the near omni-directional antenna should be used and the installer will rotate the antenna system to the upright position. The mechanical detect switch will open causing the near-omnis to be deployed. If the AP is mounted on a wall, the installer will rotate the antenna system to the horizontal position causing the detect switch to close, thus deploying the patch antennas.
The present invention enables a single product to give a UNII 1-2 access point nearly all the required antenna flexibility of enterprise 2.4 GHz access points. The present invention provides adequate diversity for 5 GHz. OFDM systems are inherently robust against multipath conditions and the packet-by-packet diversity algorithms controlled by the MAC are applicable. The MAC diversity algorithm naturally converges to the strongest antenna as the default whether it is the near omni-directional antenna or the directional patch antenna, under normal use. The present invention would provide a huge degree of application flexibility at a very lost cost, since all the antennas are constructed on a single RF circuit board.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.